Deflecting and focusing means for x-rays



Feb. 14, 1950 1.. K. FREVEL 2,497,543

DEF'LECTING AND FOCUSING MEANS FOR X-RAYS Filed Sept. 19, 1946 IN VENTOR. Lua o K. Frei/e/ A TTORNEYS Patented F eb. 14, 1950 STATES PATENTOFFICE DEFLECTING AND FOCUSING MEANS FOR X-RAYS Application September19, 1946, Serial No. 697,934

UNITED 6 Claims.

This invention relates to a medium for defleeting X-rays and to acondenser for focusing X-rays using the medium.

It has long been realized that efficient means for deflecting andfocusing X-rays would be desirable, both in X-ray therapy and X-rayspectroscopy. Thus, a convergent X-ray beam, such as would be producedby a condensing lens, should be highly advantageous in deep-therapywork. Likewise, a focusing device, by concentrating X-rays which wouldotherwise be lost, should materially increase sensitivity in X-rayspectroscopy.

Simple deflection of X-rays may, of course, be accomplished by means ofplane single crystals, such as those of sodium chloride. X-ray focusinghas been attempted by means of bent single crystals, but the amount ofbending which can be achieved is quite limited. Consequently, only asmall solid angle of a divergent X-ray beam can be subtended by the bentcrystal and hence only a minute fraction of the beam brought to a focus.

In addition, defects in the crystal induced by bending frequently causetroublesome diffraction ghosts.

In view of these considerations, it is an object of the presentinvention to provide an inexpensive medium for deflecting X-rays whichmay be simply prepared from readily available materials.

Another object is to provide a deflection medium parallel to thesurface, the piece acts, when exwhich may be easily shaped to any deCurve, posed to X-rays, like a single crystal with reinclud a full Cy soas to Subtend a large spect to the crystal plane parallel to the surfaceP Of a divergent y beam and h of the molding. A part of the beam ofX-rays an eificient X-ray ens-" A furt obiect 1s to falling obliquely onthe surface is diffracted mp i a p e apparatus for producing aaccordance with Braggs law. By curving the low convergent beam Ofmonochromatic surface of the piece concavely, convergence of Accordingto the invention, an X-ray defiecpart of the incident X ray beam may beprotion medium s P p by forming smooth" duced in a manner quiteanalogous to the consurfaced body of amorphous material having.centration of light by a concave mirror. bedded therein thin flakes ofa crystalline sub- 40 The invention may be further explained withStance, Such flakes hemg oriented Parallel to reference to theaccompanying drawing, in which the Surf ace of body conveniepfly Fig. 1is a fragmentary View of a molding press medium 15 Produced m the formof h flexlble in which a polystyrene-graphite mixture has fl f' Whlchmay be curved in any deslred man, een placed, the body of the mixturebeing shown so far as known, there may be used i iiiglgfen line to1nd1cate that it has considerable amorphous material which can be formed11 o a compact body, the term amorphous referring i 2 a Vlew 9 the.press after molding to the fact that the material shows practically 31s Verhcal Y partly in on, of no diffraction pattern to X-rays.Amorphous apparaths for prducmg convergeht mono organic plastics,particularly synthetic resinous chromatlc X'ray beam 115m? a cyhndncal rthermoplastics such as polystyrene and ethyl condenser according to theinvention, the section cellulose, are preferred because of the ease withbelhg taken along the hue of 4; and which they may be shaped by molding.Fig. 4 is a horizontal section of the same ap- The crystalline materialemployed in the illparatus, taken along the line 44 in Fig. 3.

vention should, of course, be one which can readily be converted to theform of thin flakes. In general, flakes of inorganic crystallinesubstances characterized by micaceous cleavage are preferred becausethey are most easily oriented parallel to the surface of the amorphousma terial by a simple molding operation. The term micaceous cleavagerefers to the nearly perfect basal cleavage exhibited by the micas andother minerals, by virtue of which these substances are separable intovery thin leaves. Typical of such substances are mica, talc, mercurouschloride, mercurous iodide, cadmium iodide, molybdenite, yellow leadmonoxide, and graphite.

In making the X-ray deflection medium, the amorphous material,conveniently an organic thermoplastic, e. g. polystyrene, and thecrystalline material, e. g. flake molybdenite or graphite, are groundseparately and then mixed together thoroughly. The proportion ofcrystalline material is not critical, but should be as high as isconsistent with maintaining good molding qualities. The mixture is thenmolded under heat and pressure in such manner as to cause a high degreeof lateral flow in order to orient the flakes parallel to the surface ofthe molding. The resulting product, after removal from the cooled mold,is ready to be used.

Since all flakes in the molded piece are oriented In the procedureillustrated in Fig. 1, a mixture of equal parts by weight of groundpolystyrene 5 and finely-divided flake molybdenite 6 is loaded betweenopposing flat plates 1 of a compression molding press in the form of aloose mass in whichcth'ermolybdenite flakes are inrandom orientation(Fig. 1). The plates are heated to a temperature of 80 to 125 C. andforced together to mold the mixture between them. Under; the appliedpressure, the material flows laterally,

and the lattice constants of the flake molybdenite in the medium 2|.

The apparatus of Figs. 3 and 4 thus effectively deflects a portion of adivergent X-ray beam and focuses it into a hollow convergent beam ofmonochromatic rays whichqeach'es. a focus at a point belovwth'e tubeI5.- Different wavelengths of the convergent beam may be secured byincreasing or decreasing the length of the tube I5 the action of theflowing plastic serving to turn'.

the molybdenite flakes in the direction of flow.

When compression is cmpleted..(Fig.12):, there; is obtained a thin sheet8 of-material inwhich all.

the flakes are oriented parallel to the surface of the sheet. Ingeneral, it is-desi-rabla'in'making a sheet of 0.010 inch in thickness,to start with a mass at least 0.5 inch in height.

If the flakes 6 are not, perfectly oriented in the first molding, thesheetB may be cut into strips, which can then be superposed andremolded;

The-final molded sheet, af-t'ertrimming; may

be rolled into cylindrical form and used as a f 0' cusing medium toproduce a convergent monochromatic X-rayxbeamin theapparatus of Figs. 3and 4.

In this apparatus',;X-;rays of a-whole band of wave-lengthssaregeneratedin a conventional high-.vacuum-u. X-ray tube;. 9,: such as a typeAEGl-Z50, havinga .heated cathode I0, grounded target I I, andberyllium); window I2 through which the rays issue. as.-a.adiv.ergentbeam. The.

lower "end i;of :the :tube:9 fits into. a cylindrical adapter I3 .in'one side-of. which isan opening I4 concentric. with and jlargerathan the"X-ray window I2.-

Mountedon the'adapter is.:an elongatedcylindrical lead-:alloy tube I5icosaxialzwiththe window. I2 and opening, I4; the tube beingzmade in.three: interfitting "sections.- .asxshown, for convenience.inmanufacture. In.-the upper portion of the tube I5 are .twottransverse,lead-alloy shields I6 and I1 spaced from' the window I2 :and :from.each. other. Narrowuannulanslits .dszland I91;are cut"in the shieldsco-axial withn-therwindow I2; The slits are of suchfli'ameterszas -1t0-i all? in the surface of a divergent t conerincluding.- .the window I2and having its apex at. the star-get i i; Below the lower slit I3, thewall? OfthE-tllbfll-IEiiS. thickened inwardly .toprovide;aacylindricalzsurface 2 0 which.

is co-axial with:and.intercepts..the surface of the cone defined by the.slits I8 and] A polystyrene-orientedrmolybdenite-flake flexible.X-ra-ydeflectingnsheetflt, prepared as previdusly described, isrrolled-intozacylinder and secured into :the tube 5 so :as to it snugly against.

in the tube I5and shield :22, but .a portion is.

diffracted-gar reflected in :the 'form of av convergent conicahbeamwhich is sharpened by the-1 slit -23." This difiractediportion T18 ofessentially monochromatic -X-rays, the. wavelength :ofv which fromthewindow .I2 to the deflecting cylinder 2| and correspondingly changingthe diameters of the slits I8, I9, and 23 to alter the conical angle ofthe X-ray beam; Alternatively, the deflecting sheet zl' can be'removedand a new sheet containing a different crystalline flake materialsubstituted.

The apparatus shown may be used as a source ofl a convergent X-ray beamin deep therapy, in which use it has the advantage that, by suitablychoosing the wavelength. of the convergent beam, the softer X- rays,which.xproducesserious erythema; can beeliminateda';

The foregoing descriptioniissillustrative rather.

than strictly alimitativep therinyention :being coextensive in scopewith ".thenfollowing 2 claims;

What isnclaim-ed is.::

1.: In combinationxwith a source of. a divergent X=rayiv beam;ashollow.:cylinder.formed ;of an.

amorphous. organic: plastics: having; embedded therein ':.thin .flakesiof: am. inorganicwcrystalline: substance characterized :by- 1, micaceouscleavage,

such .flakes: being; oriented :parallel to the surface of the cylinder,and a support fQr'the'cyI- inder disposed to maintain the axismf thecylinder in-linewith the X-ray source;

2.; Apparatus for -.providing-a hollow convere gent beam of.monochromaticvibrays comprisingz; awsourcei of a divergent X-rraybeam; ashield spaced from" the source and. having; therein an annulariislitLeo-axial with -the 'divergent beam, such shield-i acting- -to'restrictthe-beam to .the form-of,a.hollow-divergentccone; and an X-ray;.condenser.-.-comprising a. hollow cylindrical. formedtoiansamorphousorganicl-plastichav ing molded therein thin flakes of an inorganiccrystalline substance characterized:bytmicaceous cleavage, suchflakesebeingioriented parallel to the surface ofthe cylinder-,1 andasupport for the 3.; Apparatus for-providinga convergent X-ray, beamcomprising asourceof a divergent X-ray beam,.amountinghaving thereon?a-hollow right.-. circular cylindrical X-raydeflector-support withitsaxis in lineew-ith..the -Xrray source 1 and so spaced from-the-so11-rce.-.that the vinside surface of. :the support interceptsvthe. -X-ray,- beam, I and an Xeray-deflectorhelement lining the supportand comprising; a thin., .flexible.. sheet of an; amorphous. organic.plastic having. embedded. therein: .thin flakessofuan. inorganiccrystalline substance characterized by micaceous cleavage, such flakesbeing. .-.oriented parallel to the surface of .the. I sheet.

4; Apparatus.- for. providing .a hollow convergent beam of.monowhromatie' X-rays comprisingz. asource of'a hollowadivergent conicalX.-ray beam; a mounting havingrthereon a .hollow right-- circular.cylindricalsX-ray deflector support 00-- axialwith .the source. and-so.spaced .from= the latter that the -.inside.-.surface.of=thesupport in-.

is: fixed by the. conicaLangle ofthe divergentbeam' terceptstheshollowu. conical..-X.-ray beam, and

an X-ray deflector element comprising a thin flexible sheet molded of anamorphous organic plastic having embedded therein thin flakes of aninorganic crystalline substance characterized by micaceous cleavage,such flakes being oriented parallel to the surface of the sheet, thesaid element being curved to cylindrical form and'removably lining thedeflector support.

5. Apparatus according to claim 4 wherein the organic plastic ispolystyrene and the inorganic substance is graphite.

6. Apparatus for providing a convergent ray beam comprising: an X-raytube having an X-ray transparent window therein; a hollow cylindricalX-ray opaque tube mounted on the X-ray tube co-axial with the windowthereof, a pair of X-ray opaque shields mounted transversely in the tubespaced from the window and from each other, each shield having thereinan annular slit co-axial with the tube, the slits being of suchdiameters as to restrict the X-ray beam issuing from the window to theform of a hollow divergent cone, a cylindrical X-ray deflector supportsurface formed in the tube coaxial therewith and at a point more remotefrom the window than the shields in position to intercept the conedefined by the slits, and an X-ray deflector element comprising a thinflexible sheet molded of an amorphous organic plastic having embeddedtherein thin flakes of an inorganic crystalline substance characterizedby micaceous cleavage, such flakes being oriented parallel to thesurface of the sheet, the said element being curved to cylindricaliormand removably lining the deflector support.

LUDO K.

REFERENCES CITED The following references are of record in the file ofthis patent:

OTHER REFERENCES A Variable Temperature X-Ray Powder Camera, by W. H.Barnes and W. F. Hampton, Review of Scientific Instruments, vol. 6,November 1935, pp. 342-344.

